Physiology of StretchingTo understand the proper techniques for stretching it is helpful to know how the muscle and connective tissue respond to being stretched. There are areas within both your muscles and tendons that can sense both how quickly and how far your muscles and tendons are being stretched. These areas protect your muscles and tendons from becoming overstretched or torn during a quick stretch by causing a reflex muscle contraction. This muscle reaction is called the stretch reflex. A classic example of this is when someone taps your leg just below the kneecap. This action quickly stretches the quadriceps muscle (see Figure 7-2) and causes your thigh to contract and kick out your lower leg. The quicker the stretch, the stronger the reflex contraction. Therefore, by stretching slowly you avoid contracting the muscle you are trying to stretch! Tendons respond to stretching as well. They cause the stretched muscle attached to the tendon to relax and signal its opposing muscle to contract. This protects the stretched muscle and tendon from tearing. As a stretch is held your muscles and tendons adapt to the new length. The most effective stretches are performed slowly and are held for 10 - 30 seconds.

Flexibility ExercisesOne of the most safest and most beneficial types of flexibility exercises is static stretching. Static Stretches are slow, controlled movements through a full range of motion. The term “static” means the stretch is held at the end of the joint’s range of motion. These static exercises are considered safe and effective because they stretch the muscles and connective tissue without using fast movements that will be resisted by the muscles. These exercises can be done actively (e.g., you contract the opposing muscle group to stretch the target muscle group) or passively (e.g., you use a towel to stretch the muscle). Incorporate the static stretches in Table 9-1 in your exercise program. These exercises target the muscle groups shown in Chapter 7, Figure 7-2. Select at least one stretch for each muscle group. Hold each stretch for 10-30 seconds then rest 10 seconds. Repeat each stretch 2-5 times. Muscle balance also applies to stretching, so stretch opposing muscle groups (e.g., stretch hamstrings and quadriceps).

A second type of flexibility exercises is dynamic stretching (Table 9-2). Dynamic Stretches are controlled muscle contractions through a joint’s range of motion. These stretches should be used to enhance the performance of an activity that immediately follows the stretch; i.e., swinging your racket prior to a tennis match. This type of stretching warms the muscles. Dynamic exercises are safe as long as you do not use momentum to force a joint through a greater range of motion than it is capable. Also, avoid bouncing movements. (See page 73.)

This abandonment was is due to the attendant risks of bone conditioning. The slightest over zealousness in conditioning bony areas and the periosteum will separate from the bone because the bone becomes depressed away from the periosteum.

Once it has lifted from the surface of the bone it will lose its indirect blood supply and take a long time to re-attach. Whilst it is unattached blood will collect between the bone proper and the periosteum. This is the dreaded and very painful bone bruise. Other problems are much worse.

Complications of Over Training:

Bones: Bruised bones take a very long time to heal due to the almost non-existent blood supply. This can lead to some very potentially serious complications. The most unusual and worst these complications being Osteosarcoma or Bone cancer. This is where the regenerative properties of the bone go haywire.

In Osteosarcoma the cells change and go mad, proliferating at such a rate they destroy the bone they are supposed to be repairing. This very serious illness is often, but by no means always, set off by a severe bone bruise. Like all cancers, if it is not caught in time, it can be fatal and anyway it is always serious. In young people it is more difficult to catch as it develops at an even faster rate than adults. The other serious complication of bone conditioning is infected bones, osteomyelitis.

This is where an infection sets into the body of the bone. Its main non-surgical cause is almost always trauma. The infection will eventually ulcerate out through the skin. It too can be life threatening because it can cause blood toxicity complications and very high fevers.

It is always quite difficult to cure and will often break out again as the infection slowly smolders, undetected, through the bone. Bad bone bruises can leave areas where there is too much calcium deposited or the deposits are wrongly laid down, which may have health implications in old age.

Muscles:

Deep muscles have such a rich blood supply that they bruise easily. In fact they can bruise so badly that they become flooded with blood. This can cause the muscle to swell in its fascial covering. When this happens in the calf it can cause the blood supply to the lower leg to become shut off.

This carries the possible risk of gangrene in the lower leg if the circulation is impaired for a long period. If the blockage is total gangrene will start in less than half an hour. This condition only likely to happen in the calf and is then known as Anterior Compartment Syndrome.

It can usually be detected by acute pain in the calf itself and numbness around the second and third toes as the nerves serving those areas are similarly compressed along with the arteries. The seriousness of Gangrene does not need amplifying and it too is associated with fever.

Bad diabetics with impaired peripheral blood flow should be particularly concerned about gangrene in the foot. A very high fever associated with any bad bruise is a certain sign of serious difficulty and needs prompt investigation.

Another concern with bruises is those in the body of the large muscles themselves, usually the muscles of the thigh; Although the author has seen one in the biceps. When flooded with blood from a bad bruise haemotoma, the blood starts to form a new bone in the body of the muscle.

This is heterotopic bone formation associated with charley horse or chronic cramps it is called myositis-ossificans. The small fragments of bone in the body of the muscle cause severe pain.

The ability of the muscles to form bone in this way is a method the body has developed for reinforcing areas of high stress.

With trauma this useful ability is confused and forms bone in an inappropriate place. The chance of myositis-ossificans forming is often exacerbated by deep massage to a bruised large muscle.

I thought Bill Glasheen had different views on this?

Bill? What's the bottom line in conditioning bone_ usually the surface used as a weapon and as a blocking medium?

How do you get there safely?

Shinjio sensei has told Carlos many a time and _ that's what we practice_ bone conditioning_

I believe Breyette sensei gave a very good explanation and a safe rule to follow regarding conditioning. This was something taught to me by Tomoyose sensei as well, although I didn't listen to him and opted for breaking makiwara and ego gratifying breaking demos, way before my "bones" were ready.

When we talk about conditioning, we are talking about something that few people actually understand. Yonimine sensei said he didn't advocate the hard (very extreme) type training he did and he often pointed out that he was experimenting with how far the human body could take this type of training.

I'd be interested in learning how he feels about "bone conditioning" now that he is on the north side of 50.

Reread the post on Toyoma sensei for a very sensible approach to training. Not that many will listen, but it is the sensible approach.

What causes osteosarcoma ?The vast majority of osteosarcomas are so-called "random cases", where no specific causes or predisposing risk factors can be identified.

In young people, the development of the tumour appears to be in some way related to periods in life with rapid bone growth, hence the average for tumour development is 14-16 years. The relationship to bone growth may also be part of the explanation why osteosarcoma is slightly more common in boys than in girls. However, osteosarcoma remains an extremely rare tumour in all groups of the population, and there is no extra cause for concern in rapidly growing teenagers. The relationship between bone growth and osteosarcoma formation is thought to be due to an increased vulnerability of rapidly growing cells to damage caused by chance or by as yet unidentified factors.

Sometimes the person with osteosarcoma or the parents relate a previous injury or trauma to the development of osteosarcoma. However, medical research has not found any relationship between such injury and the risk of subsequent osteosarcoma development.

In very rare cases osteosarcoma may be related to rare genetic abnormalities or to pre-existing bone disease. The most acknowledged genetic risk factor is hereditary retinoblastoma, a tumour of the eye which develops in early childhood. In these instances the inherited gene is of a nature that predisposes to both the eye tumour and to osteosarcoma.

http://www.cancerindex.org/ccw/faq

Emphasis mine. Curiouser and curiouser - not very good English but it gets the point across.

Tracer-avid osseous lesions are usually considered to represent metastases in pediatric oncology patients. However, sites of minor, clinically occult, skeletal trauma may be mistaken for osseous metastases. Objective. The objective of this study was to review our experience with skeletal scintigraphy in pediatric oncology patients to determine specificity for metastatic disease.

The abscract concludes:

Of the 45 patients with abnormal scintigraphy, 16 (35 %) had metastases and 29 (65 %) had one or more focal benign lesions. These lesions included abnormalities due to stress/trauma (25), benign neoplasm (2), infection (3), disuse (6), surgery (10) and artifacts (4). Conclusion. The majority of scintigraphic abnormalities have nonmalignant etiologies, most commonly stress reaction and trauma. In patients without known extraosseous metastases, one or two skeletal lesions should not be assumed to represent metastatic disease.

Authors: Patricia A. Lowry and M. Cristie Carstens

So osteosarcoma seems to be primarily a pediatric concern and trauma is generally thought to be unrelated to malignant cancer but is correlated to benign growths aka "focal benign lesions." So hard conditioning can give you bumps but generally they are bumps that won't grow. Sound about right Doctor type folks?

BTW - while a little knowledge can be a dangerous thing http://scholar.google.com/ is a wonderful way to get some peer-reviewed info.